Fused electrode assembly



March 20, 1951 J. w. PosEY ET AL 2,545,629

FUSED ELECTRODE ASSEMBLY Filed Aug.y 26, 1949 Patented Mar. 20, 17951John w.l Peseysna Glen L. Weiner. Elkhart, m.,

, lne.; Elkhart, Ind., a corassignors to Durakool poration of IndianaAppli-sation August 26, 19493 serial 112,608 e creme.. (ci ittitil Ourpresent invention relates to improvements in electrode assemblies formercury switches and the like.

In the past, mercury switches have been built utilizing various means`of sealing' the bottom electrode within an open endy of a metal shellwhich mayserve as a second electrode for the switch. The mostpopularmethod has employed a Arubber sealsurro'undings thev bottom eleotrodeenel squeezed under' pressure in` assembly to providev a tight sealagainst the escape of the mercury and gases, such es hydrogen from theinterior off the switch.- Such 'a seal does not prove entirelysatisfactory; however as it is not gas tight' and"- is subjectto-oreepge during op= eraf/ion ofV themereury? switch. Recently, fusedglass has been utilized' toi-.seal theA bottom elece trede in anelectrode unitv-inlsert'ab'le` iiithe` open end of theshell casing. the'open end ofJwh-ich` ls-normally rolled overv to holdrtlie electrodeunitVtherein inassembly; *Still more recently one. of theV applicants herein,Glen L. l Wehner; disclosed a new and useful mercury switch`eonstfruetionl ln his application No; 3,704; entitled` Mer'lry Switchesand Relays?" filed? olii Jau'ry' J22, 1948;

in conjunction ill/ith` zzo-inventor' Herbert Buck-len, mi; A fused Headconstruction of. ceramic insulator holding the' elettrone pest snssealedtherewitiiby'fniolten 'glassT4 "s display that application. Ametal slevesliifoiihdlng-tlie ceramicwas fused witlfrthe lgleisssifltlenwelcled to thebuter shell0`f"`tlie'sy'vite'lrl.v Seli a structionprovided aniadequa'teseal and' sue 'ssr` fullyVr overcame the sealing?difficulties mentioned above: However, wehavemadeeertairl'improvementsovertlle construction shownV iii'-tlie'r above' mentioned applicationane'ilor't to ovec file' certainy disadvantages' thereof and toprov-idea tighter andmore efllcient seal and'grater rigidity tothe' assembledswitch. Since 'we' contemplate thefus'e-offtiie' semefofsiiriilef fire'rial's Lour varlous-switen parts, reference herein isiliaoev to theabove" pljlfd'tio'n' Serial No; $704: 6i Bucklefn and?V Welmer.- y

It an cbject'offf our invention toprcvide a new mercury'switoh orVrelay, preferably or the type constructed with ali'outermetall shellforni; ing 'one' electrode and a novele'lctrode assembly insertable ii'ari; operieifid'f of the outr Slis 7, suene assemblyA including-r4 afsecond electrode for the :switch or relasf.

inglan electrodei'nsertedirra.ceral'lilcinsulatr member, which in turnis carried by an annular.

. lays eis-esem metal sleeve with a fused glass insulating Vseal formedbetween the electrode and ceramic and between the ceramic and metalsleeve t'o form a unitary fused` li'e'ad assembly for a` mercury switchor the like that is' both rigid aliciv gas` tight.

Another object of 'our invention isto provide an 'eletrode assembly ofthe aforementionei type in which the metal sleeve surrounding theCeramic insulator inoludes a flanged eyelet pr= tion embedded in a glassbeati surrounding the electrode shan-k to provide an improved plat#Afori-n sealV toprevent escape of as or mercury from the interiori ci themercury switch and' to' give greater operating rugeclness to the asisembled switch or relay.

A further" object of our invention isr to provide a metal sleeve in' theelectrode assembly; as aforesaid, capable of holding a e'eralic iirfsulatorfin sueli-ailailfner therein asL to support it againstshk aridjarring during" activez 'o'pi ratillifthe nieruy Switch or relay.

A still further object of our invention is" to provide' eletr'dfll'adassembly; as c described above,-ul'iaviiig' the lvarious partsthereof of? lil' foereient f ther 'al' eiipjnsion toprevet their an erunder'operatig' witen or relay.v `Il-i e il othere'bjeets'L will appearfrom tie' totiiri as tlfe" fol-lowing s'peoioa'ties and' 'cleseriptiorlpr d irl order to 'dualnt those skilledi the' ri'; 'with' thev /iinei Gfee Strting' azidelltili i j "'"ioi's p si and manner oise-ailing tlieffiif'olgtl'ie'i"V unitary' head; sri-d1 Figure 's' isi-s detainee fromeleve-'tien of es alternate nea ssiriblys'ifiiifr te shown Figures Refernew'te'rig 1.--tlie switeii merel-if shown'Y of tll'enier to mercury'coiite't* ariel eoniprisesatubular metal outer shell i0 in whichanelecftro'deflassenbly, generally i-'rL riti'cetted'v at It;is'insetable.- Tlie electrode/s@ prises a hollow metal cylinder closedat one endv and provided with an open end I9` adapted to Y receive anelectrode assembly, such as is shown in Figures 2 and 3. The outer shellmay comprise one electrode of the mercury switch and is designed to beconnected in operating electric circuit by suitable means known ltothose familiar with the art. The outer shell is preferably made ofnickel or nickel-coated steel, as will more clearly appear in theoperational description hereinafter. Y :sThe electrode assembly II shownin Figure 2 displays a preferred embodiment of our invention. As seen inthat figure, an annular metal sleeve I2 has a central cylindricalportion 20, set inwardly at one end thereof to form the annular eyeletportion I6 shaped as a frustrum of a cone. An annular flange portion 2I. may be provided at the opposite end of the cylinder portion 23 fromthe eyelet and is adapted to be welded to the lower end of the outermetal shell Il! to seal over the open end I9 thereof. The sleeve may beof any suitable metal, such as steel, adaptable to beproperly welded tothe outer metal shell, and preferably having the same thermal expansivecharacteristics as the glass bead, ceramic and electrode I4.

- The ceramic insulator I3 may be made of any suitable ceramic and, asshown herein, is preferably of a dense steatite material, chief of whichis clinoenstatite crystals (MgO-SiOz). As shown in Figure 2, the ceramicis in the form of a cylindrical shell 24 of a slightly smaller outsidediameter than the inside diameter of the annular metal sleeve I2, sothat it may be inserted therein in final assembly. Oneend of theceramicrinsulatoris provided with an angular chamfer 25 `formed alongthe outer annular edge thereof; A frustro-conical bore 26 is providedinwardly' of the chamfered angular edge of the ceramic insulator, tomeet a cylindrical bore 21 extending from the opposite end of theceramic. Both the conical bore 26 and the cylindrical bore 21 aredisposed centrally of the ceramic insulator so as to provide a hollowcenter portion therefor. An annular shoulder portion 23 may be providedat theV bottom of ythe cylindrical bore 21 where it meets the conicalbore 26 for supporting the lower end of the electrode I4 insertable inthe cylindrical bore.

'As shown in Figure 2, the-electrode I4 may be composed of an uppersolid shank portion 30 and a lower cup portion 3l operatively weldedtogether so as to make a unitary structure throughout. As herein shown,the electrode structure is preferably made of nickel or nickel-coatedsteel, but may be of any other suitable electric conductor material. Inassembly, thecup portion 3| is adapted to fit within the cylindricalbore 21 of the ceramic so that the hollow center cup portion thereof isin open receiving relation with the beveled shaped conical bore 2-6whereby mercury may readily reach the electrode I4. The shank end 30 ofthe electrode I4 is shown as a cylindrical rod having a flanged end 32adapted to be Welded securely to the bottom of the cup portion 3l. Sucha bi-electrode construction is not essential however and a single-pieceelectrode may be used with equal facility.

In combining the outer sleeve, the ceramic and the electrode to form aunitary electrode assembly, the ceramic is placed with its conical boredownward and the outer metal sleeve slipped over the ceramic so that theinner edge of the veyelet portion IB rests along the upper edge -0f theceramic in a central disposition therewith. AThe bottom cup portion 3|of the electrode is then inserted into the cylindrical bore 21 of theceramic with-the shank portion 30 extending upwardly in a centraldisposition therewith. A sealing bead of fused glass 35 of a commonborosilica typehaving a fusing temperature of around 1800 F. may then beintroduced to surround the shank of'the electrode to fill in a void 36between the outer diameter of the hollow lower cup of the electrode andthe'cylindrical bore`21 of the ceramic to thereby secure the electrodeand the ceramic together in unitary relation. AIt will be noted that theeyelet portion ofthe outer shell extends inwardly toward theelectrodeshank and the fused glass is united on both sides therewith toform a platform type of seal 34 giving strength and rigidity to theassembled unit. The glass is allowed to cool in the form of a Abead 35around the shank of-the electrode. It is also desirable that the liquidglass join the ceramic cylindrical side walls to the :inner side wallsof the metal sleeve I2. `To insure such fusion, it maybe necessary toturnthe electrode assembly over to pour the glass in from-the end of thesleeve bearing theviiange 2l. It will be seen that fused glass fills inthe void, indicated generally at 36 of Figure 2, and also fuses theceramic to the outer metal sleeve by filling the void, indicatedgenerally at 31 of Figure 2. Thus assembled, an electrode unit isprovided having a metal to glass to ceramic to glass to metal sealingstructure. It should also be noted that by providing a platform seal bymeans of the eyelet embedded in the glass bead a new and useful mannerof supporting the ceramic against shock and jarring when the mercuryswitch is being operated has been provided which Ywill give the rigidityand ruggedness heretofore unpresent in switches of this type.

Referring now to Figure 3, an alternate electrode assembly II', similarto vthat of Figure 2, is shown; it will be noted that the cylindricalmetal I2 in that figure is provided with an in wardly bent annular ange22 adapted to contact the upper portion of the ceramic I3. An

eyelet I6 is formed integrally -with a flange portion 2|' in a singleannular plate welded to the upper flange 22 of the sleeve. The ceramicI3' differs from the ceramic I3 of Figure 2 in that an intermediatecylindrcalbore 23 is disposed between a frustro-conical bore 26 disposedat one end of the ceramic and a cylindrical bore 21 disposed at theopposite end of the ceramic. A shoulder 28 similar to Shoulder 28, shownin Figure 2, is provided at the ,bottom of the cylindrical bore 21 tosupport a cup portion 3| of electrode I4' similar to the cup 3I, shownin Figure 2. The upper end of the electrode I4 is provided with acylindrical rod portion 3U! similar to rod 30, shown in Figure 2, buthaving undercut detents 33intermediate its ends provided for the purposeof allowing more secure gripping of the electrode `shank by the fusedglass bead 35 in assembly. In 'assemblinga unit 5. such as is shown inFiguie 3 several noticeable dijerences over the construction of Figure 2willlbe apparent. 5i-ter insertion of the ceramic inthe metal, sleeveiz' the lower edge of the sleevis rolled over to meet the, chamferededge 2Q of the ceramic to thereby hold the two togetherV in assembly. Itwill also be noted' that the fused glass does not fill the voids betweentheV ceramic'l and the outer metal sleeve or. between the ceramic andthe cup portion 3L ofV the electrode, the construction here beingsuchthat these various parts assemble in close re ceiving relationwithone another. However, the detents providedin the electrode shank-'are gripped firmly by the fused glass bead-V to provide rigidityagainst` longitudinal jarring ofA the assembled unit. A platform seal 3e'is provided-l 'by imbedding the eyelet I-B", similar to. IB; off

Figure 2, in the fused glass. bead to perform a similar function` asthat described. in. connection with` Figure 2. It should also be. notedthat this alternate assembly provides an electrode unit havingcompactne'ssand rigidity and sealed against gas leakage from theinterior of the completed mercury switch.

Assembly, use and ogieratzonv Either electrode. assembly describedherein mayr b ej operatively joined to the outer shell I0, as bywelding, in a manner similar to that clis- 'closed` in. the Bucklen andWeimer application Serial No. 3,704 of reference herein, whereby theouter shell containing the actuating mercury body 40 is inserted betweenthe pair of welding electrodes in a gas tight chamber, the air or gasbeing evacuated from the outer shell, the electrode assembly unit beinginserted in proper position with the outer shell so that flange membersof the metal sleeve are in contact with the bottom portion of the outermetal shell and the unit thus welded together along the iiange portionof the sleeve and the 'bottom of the metal shell in an evacuatedatmosphere.' If desired, gas, such as hydrogen, may be introduced in theshell before the welding operation to provide a gaslled mercury switch.In providing an electrode assembly fused to the outer sleeve by means ofthe fused glass bead, such as has been described herein, wherein theglass fuses with both the ceramic and the metal parts to operativelyhold them in rigid assembly, it has been found desirable to constructthe metal parts coming in contact with the mercury lbody ofnickeleplated steel or of nickel metal entirely having like thermalexpansion characteristics. The desirable features obtained byconstructing the metal surfaces of such material are such that theoperating temperatures of the mercury switch are greatly reduced belowthose constructed with other classes of materials. Such a reduction intemperature rise in a switch results in the switch being able to carry agreater load without damage thereto. In addition to the strikingadvantages of reduced operating temperatures. the nickel coating ornickel parts substantially eliminate all contamination of the mercury,and further reduces the chance of burning through of the mercury in thecase of nickel-coated parts to the steel of the shell and the electrodemounted therein. Moreover, insurance against rusting of the variousmetal parts is provided by such a nickel-coating or nickel metalconstruction.

To provide such a nickel-coating on the various metal parts coming incontact with the mercury, the electrode assembly and outer metalcasings' are preferably washed ina sui-table know-ri nickel-platingbath, such as a solution of Various known compositions and combinationsof nickel chloride, nickel cyanideor nickel ammonium sulphate. It isobvious that the use oi nickel coated steel er solid nickelmay be moredesirable and more convenient and will notv depart from the spirit ofthis construction. After the various parts have been nickel coated, asdescribed above, they maybe brushed by means of stainless steel brushesbefore the electrode is assembledin the outer shell. The preferableconstruction of;Y the switch, as` described herein, is to have these'metal parts made ofv nickel or nickel coated steel. The ceramicinsulator, as mentionedv before, is preierably'of dense steatite material and the glass seals are preferablyof comw mon boro-silica typeglass, allV of which parts when assembled as an electrode u nit wi-llhave common or substantially matching thermalV expansion characteristicsover the operating temperature range to which the switch may be sub-Vjected in normal operation, so that the electrode assemblies, whenbonded together inthe manner described, will not have breaking away ofthe various parts from one another. Itis, ofcourse, understoodl thatother materials than those specified above may be used; if desired.

In operating a mercury switch of the type described"Y above, the mercuryisv normally atV the closed end of the outer shell when the switch isopen, so that there is no mercury to mercury contact across the outershell electrode and the electrode in the electrode assembly. To closethe mercury switch, the entire unit is merely tipped over so that themercury contacts the inner surface oi the outer metal shell and the cupportion of the lower electrode, thus allowing electric current to iiowbetween the two electrodes in a manner well known to those familiar withthe art of mercury switches. It should be further noted that inproviding an electrode assembly having an eyelet IS or IB', as shown inFigures 2 or 3, respectively, means have been provided for supportingthe -ceramic insulator against shock and jarring when the switch istipped over in operation, thus providing a further guarantee against thevarious parts of the assembled unit breaking away from one another.

While we have herein shown what we consider to be preferred embodimentsof our invention, it will be readily understood that numerous changesand modifications and the use of equivalents may be used withoutdeparting from the spirit and scope of this invention, and, therefore,we do not Wish to be limited to the specific embodiment hereinillustrated, except as may appear in the following appended claims.

We claim as our invention:

1. In an electrode assembly for mercury switches or relays of the typeadapted to be inserted as a unit in the open end of a tubular metalshell adapted to carry a body of mercury, an outer metal sleeve, anannular flange connected with said sleeve and adapted to be welded tothe abutting open end of said shell, an annular frustro-conical eyeletconnected to said sleeve and projecting from said sleeve in an oppositesense to said flange, a cylindrical ceramic insulator insertable withinsaid sleeve, an electrode insertable in said ceramic having .a cupportion adapted to mate with a cylindrical opening centrally disposed atone end of said ceramic and a solid shank portion rigidly attached tosaid cup portion and extending axially therefrom;

asasea 7"' and a sealing glass bead adapted to seal and bond said sleeveto said ceramic, said ceramic to said electrode, and said eyelet to saidceramic and electrode wherebyy a rigid, rugged and gas tight electrodeassembly is provided.

2. In an electrode assembly for mercury switches of the type adapted tobe inserted in the open end of a tubular metal shell, an outer metalsleeve, a ceramic insulator having a mercury receiving frustro-conicalbore at one end and a cylindrical bore at the opposite end, both boresbeing centrally disposed of said ceramic; a metal electrode having a cupportion at one end thereof adapted to be inserted in said cylindricalbore of said ceramic, an annular eyelet extending -angularly from saidsleeve and adapted to partially overlie said electrode cup assembled insaid ceramic, a flanged skirtat the opposite end of said sleeve adaptedto be welded in abutting relation with the open end of said shell, and afused glass bead forming a metal to glass to ceramic to glass to metalgas tight seal between said sleeve, ceramic and electrode, said glass`also surrounding three surfaces of said annular eyelet and bondingtherewith to provide a gas tight platform seal which furnishes shockresistance and gas tightness to said electrode assembly.

3. In a unitary electrode assembly for mercury switches or relays of thetype adapted to be inserted in the open end of a tubular mercury 30carrying metal shell, an outer metal sleeve, a combined flange and.annular eyelet member being fastened to one end of said sleeve, saidflange being adapted to abut and weld with the open end of said shell, aceramic insulatorv adapted to be inserted within said sleeve, saidceramic having a centrally disposed cylindrical bore at one end thereofand a frustro-conical bore at its opposite end, said two bores beinginterconnected by a smaller intermediate cylindri-V cal bore, and saidceramic being firmly gripped in assembly by a rolled over edge of saidsleeve -along a chamfered peripheral edge of said ceramic; an electrodeincludinga hollow cup portion adapted to be inserted in said iirstmentioned cylindrical bore of said ceramic insulator and a solid metalshank extending outwardly from lthe closed bottom of said cup portionand rigidly fsecured thereto; detents in'said electrode shank, and a,fused glass bonding seal surrounding said electrode shank and saideyelet, lling saidde -Y tents -and fusing with said ceramic to therebypravide a rigid and gas tight electrode assembly.

AJOHN W. POSEY.

GLEN L. WEIMER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Bear Oct. ,11, 1938

